Mastic gun



FIG. 1 is a perspective view of the new design for a mastic gun;

FIG. 2 is a plan view of the mastic gun shown in FIG. 1;

FIG. 3 is a side elevational view of the mastic gun shown in FIG. 1;

FIG. 4 is a rear elevational view of the mastic gun shown in FIG. 1; and,

FIG. 5 is a front elevational view of the mastic gun shown in FIG. 1.

The broken line showings are for illustrative purposes only and forms no part of the claimed design. 

The ornamental design for a mastic gun, as shown and described. 